E fficient and cost-effective electrocatalysts play critical roles in energy conversion and storage [1][2][3] . Homogeneous and heterogeneous catalysts represent two parallel frontiers of electrocatalysts, each with their own merits and drawbacks 4,5 . Homogeneous catalysts are attractive for their highly uniform active sites, tunable coordination environment and maximized atom utilization efficiency, but are limited by their relatively poor stability and recyclability. Heterogeneous catalysts are appealing for their high durability, excellent recyclability, and easy immobilization and integration with electrodes, but usually have rather low atom utilization efficiency due to the limited surface sites accessible to reactants. To this end, considerable efforts have been devoted to developing nanoscale heterogeneous catalysts that can increase the exposed surface atoms 3 . However, the inhomogeneity in the distribution of particle sizes and facets poses a serious challenge for controlling active sites and fundamental mechanistic studies 6,7 . In contrast, homogeneous catalysts typically exhibit the well-defined atomic structure with tunable coordination environment that is essential for deciphering the catalytic reaction pathway and rational design of targeted catalysts with tailored catalytic properties 8 . Single-atom catalysts (SACs) with monodispersed single atoms supported on solid substrates are recently emerging as an exciting class of catalysts that combine the merits of both homogeneous and heterogeneous catalysts [9][10][11][12][13][14] . However, most SACs studied to date employ metal oxides (for example, TiO 2 , CeO 2 and FeO x ) as supporting substrates to prevent atom aggregation [15][16][17][18] , which cannot be readily applied in electrocatalytic applications due to their low electrical conductivity and/or poor stability in harsh liquid-phase electrolytes (for example, strong acid or base). Atomic transitionmetal-nitrogen moieties supported in carbon (M-N-Cs) represent a unique class of SACs with high electrical conductivity and superior (electro)chemical stability for electrocatalytic applications 19 . In particular, Fe-based M-N-Cs have been extensively studied as electrocatalysts towards the oxygen reduction reaction (ORR) with demonstrated activity and stability approaching those of commercial Pt/C catalysts 20,21 . In addition, as suggested by numerous theoretical studies, M-N-Cs are promising candidates for catalysing a wide range of electrochemical processes, such as hydrogen reduction/oxidation 22 , CO 2 /CO reduction 23 and N 2 reduction 24 . A significant advantage of SACs is that the well-defined single atomic site could allow precise understanding of the catalytic reaction pathway, and rational design of targeted catalysts with tailored activity (in a manner similar to homogeneous catalyst design). However, this perceived advantage has been investigated theoretically

A novel superhydrophilic and underwater superoleophobic polyacrylamide (PAM) hydrogel‐coated mesh is successfully fabricated in an oil/water/solid three‐phase system. Compared to traditional oleophilic materials, the as‐prepared hydrogel‐coated meshes can selectively separate water from oil/water mixtures with the advantages of high efficiency, resistance to oil fouling, and easy recyclability.

Biological organisms with super-hydrophobic properties, such as lotus leaves, [1] cicada's wings, [2] water strider's legs, [3] and desert beetle's backs [4] always give us inspiration to design and create novel interfacial materials. Learning from nature, fabrication of micro/nanohierarchical structures and chemically modification with low surface free-energy materials provide effective solutions in obtaining super-hydrophobic interfaces.[5-9] However, superoleophobic interfaces, which display apparent contact angles with oil greater than 1508 and low hysteresis, are highly dependent on modification of fluorinated materials, [10][11][12][13][14][15] resulting in a cumbersome situation when exploring new materials. As previously reported, nearly all efforts were focused on the design and preparation of materials, that is, the control of a single phase, although the interfacial properties usually involve the interactions of two or more phases.[16] Therefore, new strategies to fabricate superoleophobic interfaces remain a challenge.As far as we are aware, examples from nature in air rather than in water environments have attracted most attention from biomimetic research on self-cleaning effect. For example, seabirds, rather than fish, are endangered by pollution from oil during a shipwreck. Boats are contaminated by plankton, while fish can keep their body clean in water. The interesting phenomenon of fish keeping their surfaces clean in oil-polluted water, a new superoleophobic model, inspires us to a novel strategy in designing superoleophobic interfaces. This bioinspired superoleophobic interface with low affinity for oil drops is better than traditional approaches commonly used, which employ surfactant solutions to aid in the removal of oils from the surfaces. [17]